The invention relates to electronic load resistors, supplied from at least one signal source, for low-power bipolar circuits and for control amplifiers and the use of these for balancing unsymmetrical signals. In amplifier circuits, load resistors are normally used for converting current to voltage by means of an amplifier element, e.g. a bipolar transistor, supplying an output current that causes a voltage drop across a load resistor that can then be used as input voltage for another amplifier stage. A differential stage supplies two output currents and normally requires two load resistors. There are also arrangements with more than two output currents. Also for the balancing of signals that are not balanced to earth, resistors embedded in an auxiliary circuit are usually used. If the objective of low current consumption is pursued here, large load resistors result in bipolar integrated circuits that take up a disproportionately large amount of space and, owing to their junction capacitance, they have an adverse effect on the frequency response. The increased space required also leads to correspondingly higher costs for the manufacture of the integrated circuit. For this reason, it has been proposed (EP 0296131) in conjunction with active filters to use a series circuit of diodes in place of a resistor. It is also possible to increase the size of a resistor electronically by `bootstrapping` (VLSI design techniques for analog and digital circuits, McGraw-Hill Book Co.--Singapore 1990, page 327).
In a series circuit of diodes, a considerable voltage is required, however, which is very undesirable in terms of total power and controllabillty. Increasing the size of a resistance by bootstrapping is not very stable and requires additional coupling capacitors, representing a conflict with regard to the desired saving in surface area.